1. Field of the Invention
The invention relates to the baking of food items, and more specifically, to controlling the types and amounts of baking energy that may reach a food item in a certain period of time.
2. Description of Related Art
Commercial food items, such as pizza products, often are baked in a metal pan that is subjected to substantial heating or baking energy. The baking energy often is supplied from both above and below the pizza by separate means, such as upper and lower sets of impinging jets of gas, such as air or superheated steam, or less rigorous means of convection heat, to name several examples of more traditional thermal-energy transfer. In the case of substantially flat, substantially planar food products such as pizza, such heat transfer generally is considered more effective if the heat is directed toward the product in a direction generally perpendicular to the plane in which the product lies. As will be described, other types of heating are also known in the art, e.g. electromagnetic radiation such as microwaves, infrared rays, and intense light within the visible spectrum, e.g. as in FLASHBAKE ovens manufactured by Quadlux, Inc., Fremont, Calif. U.S. Pat. Nos. 5,736,713 and 5,036,179 to Quadlux, incorporated herein by reference, disclose intense-light heating devices.
Heating a pizza or other food product from below often is achieved by thermal conduction through a metal pan base while the pizza is baking. Heat can be supplied to the bottom surface of the pan via convection currents of hot air (most effectively by impingement), thermal conduction from a hot oven surface, infrared rays, intense light, and/or, if the pan has a ferromagnetic component to its base, via induction. Generally speaking, however, microwave energy is ineffective to heat the food product through a metal pan surface, because the metal reflects the microwaves away, much like light from a mirror. Heating from below commonly is achieved with impinging hot air, as in the typical impingement oven.
Heating a pizza or other food product from above often is achieved by convection, as opposed to conduction. Convection heating may be effected by impingement of hot air or superheated steam, infrared rays, intense light or microwaves, to name several examples.
In the commercial pizza industry, for example in pizza restaurants and pizza delivery environments, it is generally considered desirable to achieve short baking times. This decreases customer wait time and allows more rapid oven and table turnaround. However, the speed of heat transfer in conventional baking environments (e.g. using convection, conduction, or infrared heating) is limited by conduction and the relatively slow migration of warmed water vapor from the top and bottom surfaces of the pizza into the center of the pizza. The heating process is further decelerated by the evaporation of moisture from an uncovered, baking pizza, in much the same way that perspiration cools a human body by evaporating from the skin.
In theory, the speed of heating can be greatly accelerated by simply raising oven temperature. However, if the temperature is too high, the crust of the pizza and the surface topping of the pizza may burn while the center of the pizza remains cold and insufficiently cooked, or even completely raw. The problem is heightened in that the outer rim of a pizza is particularly prone to burning and drying while generally suffering the most exposure to the sources of heat. As such, absent some other solution, baking typically has to occur at a reduced temperature, which ultimately slows the baking process.
Impingement baking has succeeded in shortening baking time, to a certain degree, by increasing the convection heat transfer coefficient without raising oven temperature. Even so, many consider impingement baking alone to be inadequate in the face of increasing consumer demand for hot, completely and evenly cooked food products in shorter and shorter time periods. In response to this pressure, microwave energy has also been used to reduce baking time. Although microwaves are able to penetrate more deeply into the center of food items that they heat, microwaves also can have the undesirable effect of supplying undesirably high heat levels to the edges of e.g. a pizza. This can result in drying and eventual burning of the crust, as well as undesirably tough textural properties, which are substantially the same problems faced when merely increasing oven temperature or applying microwaves alone.
Combining both conventional heating and microwave heating in a single oven can work to reduce overall baking time and provide other advantages. See, for example, U.S. Pat. No. 5,272,299 to Ovadia, which is incorporated herein by reference. Even with combined-heating environments like those in the Ovadia patent, however, the problems of drying, burning, and microwave-induced toughening at the outer edges of the food product, and/or rawness at the center, often still need to be addressed.
Further, the above-described advances in decreased baking time generally have not addressed the problem of baking different sized food products, e.g. large and small pizzas (which often require different amounts of heat and/or different baking times), in one oven at the same baking time and temperature. A small pizza may be burnt while a large pizza may remain uncooked if they are both baked under the same conditions of time and temperature. In the commercial environment, this can result in an excessive number of ovens or unacceptably high operational complexity.
A need has arisen in the art to address the above and other related problems. For example, there is a need for devices and/or methods that adequately reduce overall baking time while reducing operational complexity and providing even heating without burning, microwave-induced toughening, or rawness.